From Grandma Su's recipe book, page seven: "Write down what you know. Leave a little room for what you will learn."

Three days after the roof, the rain stopped, and Wenxi decided to become a businesswoman.

She had a plan, or at least the skeleton of one. It had arrived at four in the morning, somewhere between the sixth drip and the seventh, and it was so simple that she was angry nobody had thought of it before. The old town had started to fill with visitors. They came by the busload on Saturdays, in sun hats, carrying cameras, wandering up and down Sixth Alley and photographing every doorway. They bought paper fans. They bought little clay boats. And they walked straight past Su Ji, because the glass case was cracked and the sign was peeling and the pastries sat in plain white boxes with no more ceremony than a bag of rice.

Wenxi had designed cakes for hotel ballrooms. She had made a sugar peony that sold for the price of a month's rent. She knew, in her bones, exactly what a person would pay for a beautiful box.

A small line, she thought. Four or five of Grandma's best pastries, each pressed from one of the old wooden moulds, packed in a handsome box with a ribbon. A gift for a visitor to take home. Priced for what they were, not for what the street thought they ought to cost. It would not save the roof. It would not replace the oven. But it would be a start, and a start was something she could do with her own two hands, and that was a thing she badly needed to be able to do.

All she required was a few test batches. And for that she required supplies, which meant the tall cupboard above the pantry, where Grandma had said, on the phone to the grocer last week, that she kept the good vanilla and the cocoa and some other things.

She dragged the step stool across the kitchen floor and climbed up. The cupboard door was swollen with damp, and stuck so fast that she had to brace one foot against the wall and haul. It gave with a crack. A smell of dust and old spice and dried flowers rolled out and settled on her hair.

Inside, the shelves were crowded. A tin of vanilla pods. A bag of cocoa gone hard as a brick. Jars of dried osmanthus blossom, golden and faintly sweet-smelling even through the glass. A hank of twine, a tin of cutters, a canister of something that rattled. And at the very back, pushed hard against the wall as if someone had wanted it out of reach of the damp, a rectangular bundle wrapped in oilcloth and tied with string.

She knew what it was before she touched it.

The string was a knot she recognised, Grandma's knot, a flat double loop that no one else in Yunxi tied. She picked the bundle down with both hands, careful, as she might have lifted a sleeping cat, and carried it to the work table. The oilcloth crackled. Under it was a book.

It was thick and cloth-bound, the dark green of an old tablecloth, with a spine split down the middle and corners worn as soft as felt. There was no title. There had never been a title. For as long as she could remember it had lived on the shelf beside the stove, propped between the salt and the sugar, spattered and thumbed and loved, and nobody in the family had ever thought of it as a book at all. It was simply the recipes.

When had it been moved? The damp, she supposed. Grandma had put it up out of the leak, wrapped in oilcloth like a baby. She felt a pang. It was such a small, practical, tender thing to have done, and she had not even noticed the shelf was empty.

She opened the cover.

The pages were thin and brown at the edges, smelling of butter and old paper. Each one was numbered in the top corner in a small neat hand. Each one was a recipe, written in black ink, sometimes crossed out and rewritten, sometimes dotted with fingerprints of flour that had dried into the paper like fossils. In the margins were notes. Auntie Zhou likes less sugar. Double the osmanthus for the Wei sisters' birthday. Mr. Qian: no nuts, not since the spring. Whole decades of a street's appetites, recorded in the handwriting of one woman.

And at the top of every page, above the title, she saw for the first time in her life, there was a single line of writing set apart from the rest.

Sugar is the easy part. It is the waiting that makes a thing sweet.

A kitchen forgives a late riser. It never forgives a cold oven.

Dough can tell when you are angry. It will not rise for you until you stop.

She turned the pages slowly, reading them like verses. She had been a child when she last looked at this book properly, small enough to have to be lifted onto a stool to see. She had not known these lines were there. Or perhaps she had known, in the way you know the pattern of a carpet you have walked on all your life, and had never once looked down.

"Grandma," she whispered, to the empty kitchen. "You're a poet. You absolute secret poet."

The wall clock ticked. A wet pigeon hopped along the windowsill and regarded her sideways.

She turned another page, and another, and at page eleven she stopped, because the next one was thirteen.

She turned back, in case she had missed it. Eleven. She turned forward. Thirteen. Between them, close against the spine, there was a narrow ragged ridge of paper no thicker than a fingernail, the stub of a leaf that had been taken out with a blade. It had been done carefully. The edge was clean. It was not the damage of a child or an accident, not a page torn out in a hurry and lost. Someone had sat with a small sharp knife and a steady hand and removed it, as a surgeon might.

On the margin of page thirteen, in faded pencil, there was a note in Grandma's hand. It was only three words long.

See Xi Xi's, p. 12.

Wenxi's breath caught.

It was a small thing. It was her own name, in her grandmother's writing, in a place she had never expected to find it. And yet something in her chest loosened and ached all at once, like a knot being picked loose after years.

She went and found Grandma in the front of the shop, arranging the morning's mung bean cakes in the cracked glass case with the delicacy of a woman laying out jewels.

"Grandma. There's a page missing. In the book."

"Mm?"

"Page twelve. It says Xi Xi's. Is that, was that the cake? The cake you used to make me on my birthdays?"

Grandma did not turn around. Her hands, which had been straightening a row of cakes, stopped for the length of a breath, and then began again.

"Oh, that one," she said.

"I remember it. It was pale gold, and soft, and it smelled of, I don't know, honey, and something toasted. I used to eat the corners first." Wenxi stopped. Her throat had gone tight. "I never knew you'd named it after me."

"I didn't name it after you," said Grandma comfortably. "You were named after it. Your mother had a craving, the whole of the ninth month. Go and put the kettle on."

"Grandma." Wenxi laughed in spite of herself. "Where is the page?"

"Lost it years ago."

"You lost it? But it's cut out. Somebody cut it."

"Pages go missing from old books," said Grandma. She set the last cake in the case and shut the sliding door with a click. "They turn up when they are ready. You'll see."

She looked up then, and there was nothing in her face but mildness. But there was a very small pause in it, a hesitation no longer than a heartbeat, in which her eyes seemed to travel somewhere past Wenxi's shoulder, out of the shop, over the roofs, to a place a long way off. Then she smiled, and it was gone.

"Can you remember how it went?" Wenxi asked.

"My hands do. My head only remembers that it was good."

"Then I'll rebuild it."

"Mm," said Grandma, in a voice that managed to be encouraging, sceptical, and faintly amused all at once. "Do mind the flour. It's dear this year."

The first attempt was a brick.

She made it that afternoon, working by memory and instinct, the way she had made her first plum-blossom cakes at the age of eighteen. Eggs, sugar, a little osmanthus honey, rice flour and wheat flour in some proportion that felt right. She whipped, folded, poured, and slid it into the old oven, and while it baked she stood with her arms crossed, watching the glass, with the hungry attention of a woman who has staked her self-respect on a sponge.

It came out the colour of a paving stone and as dense as one. She cut it in half. It was dry all the way through.

The second attempt was tender at the edges and raw in the middle. She had overcorrected. She had cut the flour, added an extra yolk, opened the oven door too early, and the whole thing had sighed and subsided into a damp golden crater. She tasted it. It tasted of eggs and apology.

The third attempt she did that evening, after the shop had closed and Grandma had gone out to her weekly game of mahjong at the Wei sisters', with a flask of tea and a small bag of sunflower seeds and an air of lofty indifference. Wenxi had the kitchen to herself. She rolled her sleeves to the shoulder and tied her hair up in a cloth. She thought: I have made a three-tier cake for four hundred guests in a hotel with a broken air conditioner. I can make a cake that I ate when I was six.

It was a point of principle by now. She weighed every grain. She tested the oven with her hand, with a thermometer, with her cheek. She whisked until her arm trembled. And when the cake finally came out of the oven she stood over it with her heart in her mouth, and watched it sink, slowly, like a ship in a film, into the middle of the pan.

She said a word that Grandma would not have approved of.

There was flour on the table, on the floor, on the window. There was flour on the ceiling, and she genuinely did not know how. Three failed cakes stood in a row on the cooling rack: one flat as a coaster, one cracked across the top, one with a hole in the middle you could have lost a thumb in. Her apron was streaked with batter. There was a smear of honey on her chin. She stood with a whisk in her hand, held like a sword, and glared at the whole sorry business with her jaw set and her eyes stinging.

A knock sounded at the back door.

She did not hear it at first. It came again, three firm raps, and then the latch lifted, and the door swung open on the dusk and the smell of damp earth and jasmine.

"Zhaoyu said you were asking about a price board," said Chengyan.

He stood on the step with a wooden frame under one arm. It was a plain rectangle of pale cedar, about the size of a school slate, grooved along the inside for sliding slats, the corners mitred so cleanly she could not see the joints. He had clearly come straight from work. His sleeves were rolled to the elbow, and there was a pencil behind his ear.

He took in the kitchen.

Her whole face went hot. She saw it as he must have seen it: the drifts of flour, the bowls stacked in the sink like a failed dam, the three disasters on the rack, and herself in the middle of it with a whisk and a streak of honey and, presumably, flour in her hair.

"Don't," she said.

"I haven't said anything."

"You're doing it with your eyebrows."

He lowered them with great deliberateness. It was somehow worse.

"I was only going to say," he said, "that I can come back."

"You don't have to come back. Put it down. It's, thank you. It's lovely. The board." She flapped the whisk at the wall. "Just lean it there, I'll sort it out."

He leaned the frame against the wall by the door. Then he stood for a moment with his hands at his sides, looking around, and she thought, he is going to go. He is going to say something dry and go.

Instead he walked to the sink, rolled up his sleeves another inch, and began to wash the bowls.

"You don't have to..." she said.

"Mm."

"That is still not a word."

He did not answer, but his shoulders moved, very slightly, in what might, in a less disciplined man, have been a laugh.

They worked without speaking. It was extraordinary how easy it was. She wiped down the table, and he stacked the clean bowls on the rack. She swept the flour from the floor into a heap, and he fetched the dustpan from behind the door without being told where it was. Once she reached for the dishcloth at the same moment as he did, and their fingers collided on the damp cotton, and both of them let go as if it were hot. Neither of them said a word. He passed her the cloth. She took it. The tap ran.

The flour stopped being a disaster and began to look like a snowfall. Outside, it had gone fully dark, and a frog in the canal started up a slow, hoarse song.

"Which one's the worst?" said Chengyan, at last, looking at the rack.

"All of them."

"Which is the worst of all of them?"

She sighed, and pointed at the one with the hole.

He picked up a knife, cut off a wedge from the third cake, the sunken one, and held it in his palm. He looked at it for a while, the way he looked at a joint that had not come out true. Then he put it in his mouth.

"Wait," said Wenxi. "You don't have to eat that."

He chewed. It took a long time. His face, in the lamplight, was grave as a judge's. She watched his jaw work, and the shift of his throat as he swallowed, and the whole business of it, so earnest and so slow, was so ridiculous that a bubble of laughter rose up in her and refused to be pressed down.

"Well?" she said.

"It's structural."

She burst out laughing. It came out of her suddenly and entirely, helpless and loud, bent over the table with her hands pressed to her stomach. "Structural. Oh, my goodness. You could build a bridge with it."

"I wouldn't put a lorry on it."

"Oh, stop."

"It's good for shelves."

"Stop, stop." She wiped her eyes with the back of a floury wrist, and left a long white streak across her cheek, and when she looked up he was watching her, and the amusement in his face had softened into something she did not know how to name.

Then it passed, and he looked down at the cake in his hand and said, more quietly, "It's too eager."

"Too what?"

"Eager." He turned the wedge over. "You're trying to make it right. Every bit of it. You can taste it. Your grandmother never tries to make a thing right. She just makes it, and waits."

The laughter went out of Wenxi like water through a sieve.

It was only a remark about cake. He had said it lightly, the way a man says that a plank needs more sanding. But it landed somewhere low and tender, in the place where all the other things lived: the email in the grey font, the offset spatula in the cardboard box, the nine days of saying fine to a train window. Trying to make it right. She had been doing it since she was eighteen. She had never once let a thing sit and wait.

He saw her face. She watched him see it.

"I meant the cake," he said.

"I know what you meant," said Wenxi, very quietly.

They looked at each other across the clean table with the frogs singing outside, and for a moment the whole kitchen seemed to be holding the one breath.

Then he set the rest of the cake carefully on the rack, as if it were something worth saving, and wiped his fingers on a cloth.

"The board's cedar," he said. "It'll want oiling. Once a year. Thursday, the beam."

"Chengyan, thank you. For the board. For, all this."

"It's a frame," he said, as though that settled it, and went out of the back door and into the dark.

The latch fell. His boots crossed the courtyard, and she listened to them until they were gone.

She stood very still in the middle of the kitchen with the whisk still in her hand. There was a taste in her mouth of honey and eggs and failure, and underneath it, bright and unaccountable, something that was not failure at all.

A board creaked in the passage.

She turned her head.

Grandma Su stood in the doorway to the front of the shop with her mahjong bag over one arm and a pencil behind her ear, still wearing her good dark coat, and from the look of the damp on her shoulders she had been standing there for some time. She was smiling. It was not an ordinary smile. It was the smile of a woman who has just seen a pot come to the boil exactly when she said it would.

"You're back early," said Wenxi.

"The Wei sisters were cheating." Grandma crossed the kitchen, set down her bag, and took the sunken cake from the rack. She looked at it with great tenderness. She did not taste it. "You've flour in your hair, Xi Xi."

"I know."

"A great deal of it."

"Grandma, how long were you standing there?"

"Oh," said Grandma, vaguely, and patted her cheek with a hand that smelled of tea and sunflower seeds. "I only came to see whether the dough had risen. It doesn't, you know, when it's being watched. So I stood out of the way."

She went off down the passage, humming. It was a wedding song. It was always a wedding song.

Wenxi pulled the cloth from her head and stood in the quiet kitchen with the flour falling around her like small, slow snow. Against the wall, beside the back door, the cedar frame leaned in the lamplight. It smelled of sunshine and resin. She went across, without meaning to, and laid one hand on the smooth pale wood.